This invention relates to a demodulating system for demodulating a modulated signal produced by modulating a carrier signal by error correcting coded transmission data.
A conventional demodulating system comprises an adaptive equalizer for adaptively equalizing the modulated signal into an equalized signal in accordance with polarity signals and discrimination error signals. A demodulator demodulates the equalized signal into demodulated signals and the discrimination error signals. The demodulated signals comprise polarity bits and other data bits. Supplying lines supply the polarity bits to the adaptive equalizer as the polarity signals. An error-correcting decoder is supplied with the demodulated signal and produces error location signals representative of location of error in the demodulated signals, and corrects error in the demodulated signals by using the error location signals into decoded signals.
As will later be described more in detail, the conventional demodulating system is defective in that the adaptive equalizer can not remove distortion which appears in a propagation path because the discrimination error signals have a wrong value under the influence of big thermal noise which is inevitably superposed on the demodulated signal while propagated through the propagation path to the demodulating system.